Strength Of Denture Base Resin Research Articles

The stain resistant effect of an ultraviolet curable coating material on denture base resin.

This study aimed to evaluate the effects of an ultraviolet (UV) curable coating material on denture base resin. The results of the three-point bending test showed no significant difference between treated and untreated specimens, suggesting that the UV curable coating material did not compromise the physical strength of denture base resin. The surface free energy measurement and the surface analysis with atomic force microscopy revealed superhydrophilicity and a regularly arranged structure on the coating surface, improving wettability. Moreover, untreated specimens were significantly discolored in the staining test. However, specimens treated with the UV curable coating material showed no significant difference in color with slight staining, suggesting excellent antifouling ability. Therefore, the UV curable coating material used in this study could contribute to simplifying hygiene without altering the physical properties of denture base resins.

Influence of Thermocycling and Surface Treatments on the Flexural Strength of Denture Base Resin: An In Vitro Study.

The purpose of this study was to evaluate the flexural strength of heat polymerized denture base resin after thermocycling and different surface treatments done prior to repair or relining. In this in vitro study, 80 specimens were made with heat-polymerized denture base resin and thermocycled (500 cycles between 5 and 55 °C). The specimens were divided in four groups based on different types of surface treatment: group I (control group: without surface treatment), group II (chloroform for 30 seconds), group III [methyl methacrylate (MMA) for 180 seconds], and group IV (dichloromethane for 15 seconds). The flexural strength was assessed using a Universal testing machine with three-point bending test. The obtained data were subjected to statistical analysis using one-way ANOVA and post-hoc tests. The values of average flexural strength of denture base resin measured were as follows: group I: 111.1 MPa, group II: 86.9 MPa, group III: 73.1 MPa, and group IV: 78.8 MPa. Groups II and IV possessed superior flexural strength than group III. The maximum values were observed with the control group. The flexural strength of heat-polymerized denture base resin gets affected by different surface treatments done prior to relining procedures. Lowest flexural strength was obtained when treated with MMA monomer for 180 seconds as compared to the other etchants used. Prior to denture repair procedures, operators must choose the chemical surface treatment judiciously. It should not affect the mechanical properties such as flexural strength of denture base resins. Reduction in flexural strength of polymethyl methacrylate (PMMA) denture base can predispose the prosthesis to deteriorated performance when in function.

The Effect of Sandblasting on Bond Strength of Soft Liners to Denture Base Resins: A Systematic Review and Meta-Analysis of In Vitro Studies.

Objectives This study aimed to evaluate the effect of sandblasting on the bond strength of denture base resin to soft liners. Materials and Methods This report follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Embase, Cochrane, Scopus, and OpenGrey databases were searched for in vitro studies that compared sandblasting with no treatment in terms of the tensile, shear, and peel bond strength of resilient lining materials (acrylic-based or silicone-based) to polymethyl methacrylate denture base resin. Based on the outcome, the analysis was carried out in three groups of tensile, shear, and peel bond strength. Subgroup analysis was done for the effect of size of particles on sandblasting, blasting pressure, and type of soft liner whenever possible. Heterogeneity was evaluated among the studies, and meta-analysis was performed with random effect models (p < .05). Results After screening, 16 articles met the inclusion criteria for meta-analyses. No treatment showed significantly higher tensile (p < 0.001) or peel (p=0.04) bond strength, although shear bond strength of sandblasted resin was significantly better (p=0.008). Results of subgroup analyses of particle size favored the control group in 50 µ Al2O3 particle size (p < 0.001). In analyses of blasting pressure, the control group had significantly better tensile bond strength than specimens with blasting pressure ≤1 bar (p < 0.001) while specimens with blasting pressure beyond 1 bar showed significantly more tensile strength than control group (p=0.03). In silicon-based liners, groups without any surface treatment had significantly higher tensile bond strength (p < 0.001). Conclusion According to the in vitro studies, sandblasting would not lead to significant increase in bond strength of soft liner to the denture base resin.

Evaluvation of The Transverse Strength of Acrylic Denture Base Resins Repaired by Different Materials: An Invitro Study

AIMS: The aim of the study undertaken was to evaluate an effective method of denture repair, which will have considerable transverse and impact strength, quick to repair and can be effectively utilized by the general practitioner.&#x0D; OBJECTIVES: 1) To evaluate the transverse strength of denture base resin repaired by different methods having 45° joint surface contours and compare it with denture base acrylic resin repaired by conventional methods.&#x0D; 2) To find out the best material for repair.&#x0D; MATERIAL AND METHODS: For the purpose of this study, Heat cure resin (DPI), Autopolymerising resins (DPI) and Glass Fibers (interling), were taken from the market. The unrepaired conventional heat cure denture base resin (DPI heat cure) plates were used as control group. . &#x0D; RESULTS:&#x0D; 1) The mean transverse and impact strength of all the samples repaired by various methods showed significantly lower strength than control group (heat cure unrepaired samples used as control for transverse strength) 103.33MPa, although statistically significant.&#x0D; 2) Specimens repaired by self cure resin with glass fibers having 450 bevel joint showed the highest transverse strength.&#x0D;

English

BACKGROUND Polymethyl-methacrylate (PMMA) resin is the most commonly used denture base material which satisfies colour stability, aesthetic demands, accurate fit, affordable cost, and ease in manipulation. The common disadvantages are incomplete flow, impact strength, transverse strength and fatigue resistance. The fracture of denture base is mainly due to flexural fatigue failure which can be minimised by reinforcing with various artificial and natural fibres. There are very few studies which have incorporated natural fibres to enhance the strength of PMMA resin. So, in this study both natural and artificial fibres were used to enhance the property and find the best fibres to strengthen the denture base. METHODS A total of 80 samples were prepared using a standardized stainless steel metal die and these samples were grouped into Group A as control group, Group B PMMA samples reinforced with raw teak wood fibres, Group C reinforced with alkali treated teak wood fibres, Group D reinforced with heat treated teak wood fibres and Group E samples were reinforced with Ultra-High molecular weight (UHMW) polyethylene fibres and processing was carried out by conventional method. The flexural strength of each sample was calculated. RESULTS The mean flexural strength of Group A, Group B, Group C, Group D and Group E were 82.338, 58.680, 62.259, 105.878, 90.2263 respectively with a P value of 0.001. Group D samples showed a P value &lt; 0.001 which was statistically significant when compared to other groups. The obtained values were statistically analysed by oneway ANOVA and Tukey’s HSD test using statistical software SPSS 17. CONCLUSIONS This in-vitro study infers that the samples of Group D incorporated with heat treated teak fibres had shown increased flexural strength, which could be a good replacement for various synthetic and natural fibres to enhance the strength of denture base resins. KEY WORDS Teakwood Fibres, Heat Treatment, Alkali Treatment, Sandwich Technique, Polyethylene Fibres

Comparative evaluation of bond strength of denture base resin to acrylic resin teeth following different surface treatments: An In vitro study

Acrylic resin denture base material has been available to the dental profession for over 60 years, and although materials with superior properties have been on the market for some time, it still remains the most popular choice of clinicians. The requirement of the simple processing equipment and low cost of the fabrication process are the reasons for its continued popularity. However, debonding of acrylic teeth from denture base resins remains a problem for both patients and clinicians. The failure rate of acrylic dentures resulting from fracture has been reported to be unacceptably high, with the most prevalent type of failure documented being debonding or fractures of the teeth A series of studies have attempted to determine the quality of denture tooth bonding produced by commonly employed dental laboratory conditions. The present study was under taken to evaluate and compare the effects of chemical and mechanical treatment of the ridge lap surface of acrylic teeth on the bond strength of acrylic resin teeth to denture base resins.

Estimation of IZOD impact strength between different concentrations of chitosan-reinforced denture base resins.

Poly-methyl methacrylate (PMMA) is an universally acceptable denture base material. Efforts are made to increase the applications with the addition of new constituents. Chitosan has established antifungal properties. The mechanical properties of Chitosan-denture base composite is less evaluated in the literature. This study estimates the differences in impact strength of material for different concentrations of chitosan-reinforced denture base resins. The study estimated the differences in IZOD impact strength of denture base resin reinforced with 0%, 5%, 10% and 15% of chitosan by weight. The acrylic samples were fabricated in according to ISO 180 regulations. The study had four test groups (n = 10). ACh0 was the control group with no reinforcements. ACh5, ACh10 and ACh15 had chitosan reinforcement of 5%, 10% and 15% by weight. The samples were processed by conventional heat polymerization cycle and tested in IZOD impact testing machine. The data were recorded and statistically analyzed with Kruskal-Wallis test. The mean impact strength was high in ACh5 (4.25 ± 1.05 kJ/m2) compared to ACh0 (2.88 ± 0.60 kJ/m2), ACh10 (3.63 ± 0.40 kJ/m2), ACh15 (3.38±0.60 KJ/m2). Statistically significant differences between the test groups was determined by Kruskal-Wallis and post hoc Bonferroni test (Chi-square = 12.843, P = .005, df = 3). The impact strength of denture base resin increased with 5% chitosan compared with other percentage of chitosan. No statistical significant relationship was observed between the groups.

AN IN VITRO STUDY TO ASCERTAIN THE TRANSVERSE STRENGTH OF DENTURE BASE RESIN REINFORCED WITH TWO DIFFERENT FIBERS AND THEIR COMBINATION

&#x0D; &#x0D; &#x0D; Purpose: The purpose of this study was to compare the transverse strength of denture base resin reinforced with two distinct fibers and their combination with the denture base resin without any reinforcement. MaterialsandMethod: Atotal40testsamplesofclearheatcureresinwerefabricatedwiththehelpofa customized metallic die and divided in to four groups- Group1: samples fabricated with clear acrylic resin without any reinforcement(Control group),Group2: samples reinforced with carbon fiber epoxy resin composite block, Group3: samples reinforced with glass fiber epoxy resin composite block, Group 4: samples reinforced with combination of carbon and glass fiber epoxy resin composite block. After finishing and polishing all the samples were having final dimension of 3 cm × 1 cm × 0.3cm with a ±0.02 error measured with digital vernier caliper. Samples were immersed in water for 7 days in an incubator. A 3-point bend test was done in a universal testing machine, and load to fracture was recorded (MPa). Statistical analysis was performed using one way analysis of variance (ANOVA) followed by tukey HSD post-hoc test to compare mean transverse Strength in four groups.&#x0D; Results: Group 2 and group 4 showed highest strength with significant difference with all other groups and non-significant with each other. Group1(control group) showed lowest transverse strength among all the groups.&#x0D; Conclusion: carbon fiber and glass fiber alone provided either good transverse strength or good esthetics respectively while unique combination of carbon and glass fiber epoxy resin composite significantly increased the transverse strength of acrylic resin along with good esthetics.&#x0D; &#x0D; &#x0D;

Effect of titanium dioxide nanoparticle reinforcement on flexural strength of denture base resin: A systematic review and meta-analysis.

The study was designed to assess the change in flexural strength of unmodified heat cure denture base polymer resin on reinforcement with titanium dioxide nanoparticles in different concentrations. In vitro, randomized control trials reporting flexural strength of titanium dioxide nanoparticle reinforced resin were selected. The review was formulated based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses- Protocol (PRISMA-P) guidelines. Quality assessment was performed according to Consolidated Standards Of Reporting Trials (CONSORT) guidelines and risk of bias Cochrane tool. Six articles in the category of 1%, 3%, 5% weight fractions of titanium dioxide nanoparticles were subjected to a meta-analysis. A meta-analysis was performed using random-effects at a 95% confidence interval. Within the limitations of the study, it can be assumed that there is no precise conformity on the ideal titanium dioxide nanoparticle concentration required to improve the flexural strength of the polymer. Stringent use of standard ISO guidelines may help in obtaining consistent results.

Influence of Different Repair Acrylic Resin and Thermocycling on the Flexural Strength of Denture Base Resin.

Background and Objectives: Fractured acrylic denture base is a common occurrence in clinical practice. The effective denture repair procedure is cost-effective, time conserving, and results in lesser time without denture for the patient. Along with various reinforcements and surface modifications; different acrylic resins are investigated in improving the flexural strength of the fractured site. The aim of this study was to evaluate the flexural strength of a polymethyl methacrylate (PMMA) denture base repaired with heat-polymerized (HPA), auto-polymerized (APA) and light-polymerized acrylic (LPA) resins after thermocycling. Materials and Methods: Forty rectangular shaped (50 mm × 25 mm × 3 mm) PMMA specimens were fabricated. Group 1 specimens (n = 10) were kept as controls and the remaining 30 samples were sectioned at the center with a repair site dimension of 3 mm. The samples from three groups (n = 10) were repaired with HPA, APA, and LPA resins, respectively. The specimens were thermocycled for 5000 cycles and subjected to a three-point flexural test. The maximum load required to fracture the specimens was recorded, and further analyzed with ANOVA and the Games-Howell Post hoc test at the significance level p = 0.05. Results: The average maximum load and flexural strength of the control group was 173.60 N and 13.02 Mpa and corresponding values for denture repaired with HPA was 87.36 N and 6.55 Mpa. The corresponding values for APA resin and LPA resins were 62.94 N, 57.51 N, and 4.72 Mpa, 4.06 Mpa, respectively. Conclusions: The PMMA specimens repaired with HPA resins resulted in a significantly higher load to fracture compared to APA resin and LPA resin.

Impact of Surface Treatment with Different Repair Acrylic Resin on the Flexural Strength of Denture Base Resin: An In Vitro Study

The aim and objective of the present study was to assess the flexural strength of denture base resin based on surface treatment with different acrylic resin repair materials. Totally, 120 heat-polymerized polymethyl methacrylate denture base resin materials which are rectangular shaped with the size of 65 mm × 10 mm × 2.5 mm were fabricated. 150 μm-sized alumina used for surface treatment. All the 120 heat-cured, surface-treated acrylic denture base resin samples were randomly divided into three groups. Group I: glass-fiber-reinforced auto-polymerizing acrylic resin, group II: auto-polymerizing acrylic resin, and group III: light-cured acrylic resin. A universal testing machine was used to test the flexural strength of the repaired specimens. A highest mean flexural strength (88.96 ± 0.31) was demonstrated by group I, followed by group II (72.18 ± 1.86) and group III (66.30 ± 1.02). ANOVA demonstrated a statistically significant inter-group difference. On multiple comparisons, using Tukey's post hoc test a statistically significant difference between groups I and II and between groups I and III was found. After considering the limitations, the present study concluded that the highest flexural strength is shown by glass-fiber-reinforced auto-polymerizing acrylic resin than by auto-polymerizing acrylic resin and light-cured acrylic resin. Denture repair comprises of joining two fractured parts of a denture with a denture repair material. The success of denture repair depends on the adhesion phenomenon. The treatment of the surface can be accomplished using a suitable material which changes chemically and morphologically and thus promotes better adhesion.

Comparison of ISO and ASTM standards in determining the flexural strength of denture base resin.

The aim of this study was to compare the differences between the ASTM D790 and ISO 20795.1.2013 standards in evaluating the flexural strength of heat cure poly methyl methacrylate (PMMA) denture base resin. 30 heat cure denture base samples were fabricated in accordance to ISO 20795.1.2013 and ASTM D790 Standards. The specimens were finished and stored following the standardized protocol. The flexural strength was determined using universal testing machine at cross head speed of 1.50 mm/min and a span length of 40.00 mm. The mean flexural strength values were calculated in megapascals (MPa), and statistically analyzed. The mean flexural strength of heat cure PMMA found with ISO and ASTM ranged between 60.492 MPa and 61.470 MPa. There was no significant difference between the two methods. The quantitative differences existed in the flexural strength of denture base resin between ISO 20795.1.2013 and ASTM 790 protocols but those differences had no statistical and clinical significance.

Effect of Mechanical Surface Treatment on the Tensile Bond Strength of Repaired Acrylic Denture Base Resin Cured by Two Different Techniques

Objective: To evaluate and compare the effect of mechanical surface treatment (groove, aluminum oxide particles)with 45 degree bevel type of joint on tensile bond strength of acrylic specimens repaired by two curing methods(microwave and water both).Methodology: Eighty specimens (80) were prepared from pink heat cure acrylic resin. They were divided into twomain groups (40 specimen repaired by microwave energy and 40 specimens repaired by water bath method).Eachgroup can be divided into four subgroups of ten according to the surface treatment. The control group A was leftintact, group B received no surface treatment, group C and D received surface treatment by (groove, 50 m aluminumoxide particles). Specimens were tasted by using an instron universal testing machine until fracture occurs.Result: The results indicate that nurses have adequate knowledge toward general information on infection, infectioncontrol strategy, causes, prevention, sterilization and disinfection, and healthy conditions in operating roomenvironment. Regarding practices, the results indicated inadequate practices concerning the standard precautionduring wearing operation clothing, patient's preparation, and hand washing practices. While, their practicesconcerning tools and equipment preparations were adequate. There is a significant relationship between nurses’knowledge and practices and their educational level and years of experience.Recommendation: It can be concluded that mechanical surface treatment prior to denture base repair resulted in asignificant improvement the tensile bond strength of denture base resin.

Tensile Strength of Denture Base Material Reinforced With Zirconia Nanoparticle and Glass Fibers

ABSTRACT Purpose: The current study was conducted to determine the effect of hybrid reinforcement with zirconium oxide nanoparticles (NZ) and glass fibers (GF) on the tensile strength of denture base resin. Materials and methods: Different ratios of NZ/ GF were added into resin at a fixed concentration of 5% by weight. For each formulation (one control and 7 experimental groups), ten specimens were prepared in a dumbbell shape using a stainless steel mold. Tensile strength was evaluated by using a universal testing machine. Scanning electron microscope (SEM) was used to study the fractured surfaces. Results: Tensile strength of the specimens reinforced with NZ/GF in varying ratios was found to be higher than that of the control group. Among the hybrid groups, the specimens reinforced with 50%NZ-50%GF showed the highest tensile strength. SEM fractographs showed multiple lamellae displayed surface, which is characteristic of strong material. Weak adhesion and pull out of fibers from the matrix were seen in high concentration GF. Conclusion: The incorporation of 50%NZ-50%GF into acrylic denture base appeared to improve the tensile strength.

EVALUATION OF THE MECHANICAL PROPERTIES AND RESIDUAL MONOMER CONTENT OF COPOLYMER ACRYLIC RESINS POLYMERIZED BY DIFFERENT METHODS

Background:The aim of this study was to evaluate the effect of adding four different monomers on the flexural strength, elastic modulus, impact strength and residual monomer content of denture base resins polymerized by copolymerization mechanism.Methods:Butyl methacrylate (BMA), Isobutyl mathacrylate (IBMA), 2-hydroxyethyl methacrylate (HEMA) and methacryl-polyhedral silsesquioxane (POSS-MA) were added to monomers of conventional heat (HP) and microwave polymerized (MP) polymethyl methacrylate (PMMA) resin at the concentrations of 2%, 5% and 10% per volume. The flexural strength, elastic modulus and impact strength of specimens were measured with an universal testing machine and Charpy-type impact tester. Residual monomer contents were determined by high performance liquid chromatography (HPLC) method. Results:10% IBMA and 10% HEMA enhanced the flexural strength of HP resin. For the elastic modulus of MP resin, significant differences observed between the control group and 2 and 5% IBMA, 5 and 10% HEMA, and 5% POSS-MA groups (P&amp;lt;.05). Copolymerization mechanism had no positive effect on the impact strength of denture base resins. Significant differences were observed between the residual monomer of control group and 10% IBMA, 10% BMA, 10% POSS-MA groups of HP resin (P&amp;lt;.05). In MP resin group significant differences were observed between control group and 5% IBMA, 2-5-10% HEMA groups (P&amp;lt;.05).Conclusions: Copolymerization process was effective on the flexural strength of HP denture base resin with 10% IBMA and 10 % HEMA. However the process caused an increase in the residual monomer content of some resin groups. Keywords: Denture base resin, copolymer, flexural strength, impact strength, residual monomer.

Comparative Evaluation of the Strength of Denture Base Resin repaired with Glass Fiber-reinforced Acrylic Resin: Anin vitroStudy

The present study aimed at evaluating and comparing the transverse strength of heat polymerizing acrylic resin samples repaired using glass fiber-reinforced autopolymerizing acrylic resin with varying gap widths at the fracture site. Heat polymerizing acrylic resin samples of dimensions 65 * 10 * 2.5 mm each were fabricated. Ten of these were used as control. In the rest of samples, two grooves were fabricated and surface treated with ethyl acetate. The repair gap width was standardized at 4, 3, 2, and 1 mm. Totally, 80 samples were equally divided into these four groups. Glass fiber-reinforced autopolymerizing acrylic resin was used to repair these samples. The repaired samples and the control groups were subjected to three-point bending test, and the findings were analyzed statistically. It was observed that with increase in gap width, their transverse strength decreased. Most of the fractures occurred at the joint interface of parent and repair material. The fracture within the repaired material occurred highest in the group that had 4 mm gap, followed by groups that had 3 and 2 mm gaps. In the group with 1 mm gap, there was no occurrence of fracture within the repaired material. To achieve optimum repair strength of a repaired denture, the gap width should not be greater than 1 mm. The study will aid in determining the ideal gap width for denture repair to prevent fracture and also the clinical application of glass fiber-reinforced autopolymerizing acrylic resin.

Flexural Strength of Surface-Treated Heat-Polymerized Acrylic Resin after Repair with Aluminum Oxide-Reinforced Autopolymerizing Acrylic Resin.

Background:A fracture of denture base in situ often occurs through a fatigue mechanism, which over a period of time leads to the formation of small cracks, resulting in fracture.Aim and Objective:To evaluate the flexural strength of repaired heat-polymerized acrylic resin, with different percentage of aluminum oxide (Al2O3) added to the repair resin and effect of two different surface treatments on the flexural strength of repaired heat-polymerized acrylic resin and also to evaluate quantification of filler particles using scanning electron microscopy.Materials and Methodology:Fifty specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association specification no. 12 (65 mm × 10 mm × 2.5 mm). Al2O3<50 nm particle size was silanized using metal alloy primer before incorporation in polymer. Two different percentages of Al2O3 nanoparticles, that is, 1% and 1.5% were added to autopolymerizing acrylic resin which was used as repairing material.Results:The study showed that repair resin incorporated with 1.5% Al2O3 in the group surface treated with silicon carbide paper improved the flexural strength of denture base resin. A proper filler distribution and deep penetration within the polymer matrix were observed by scanning electron microscope in the same group.

Effect of different edge profile, surface treatment, and glass fiber reinforcement on the transverse strength of denture base resin repaired with autopolymerizing acrylic resin: An In vitro study

Background: This study is an effort to find the appropriate edge profile and surface treatment during repair of the fractured dentures, which can provide long-lasting results and can prevent the recurrence of the fracture. Objectives: The objective of this study was to evaluate the transverse strength of butt versus bevel edge profile with surface treatment and reinforced with glass fibers using autopolymerizing acrylic resin and to compare the samples surface treated with ethyl acetate and reinforced with glass fibers on butt and bevel edge profile. Materials and Methods: This study consisted of a sample size of 105, wherein 15 unfractured heat polymerizing acrylic resin samples were used as a control, 45 repaired samples of bevel edge profile, and 45 repaired samples of butt edge profile. These samples were further subdivided into groups and repaired using autopolymerizing acrylic resin, glass fiber-reinforced autopolymerizing acrylic resin, and with glass fiber-reinforced autopolymerizing resin surface treated with ethyl acetate, respectively. The repaired samples were tested for transverse strength on an Instron testing apparatus. The P value set at 0.05. Analysis was done using analysis of variance and Tukey's honest significant difference test. Transverse strength of samples, repaired after ethyl acetate surface treatment, was higher when compared to untreated samples (P = 0.001). Transverse strength of samples, repaired with ethyl acetate surface treatment and glass fiber reinforcement material, was the highest (P = 0.001). Conclusion: Ethyl acetate surface-treated bevel edge profile acrylic strips repaired using glass fiber-reinforced autopolymerizing acrylic resin showed greater transverse strength.

Flexural properties and impact strength of denture base resins reinforced with micronized glass flakes.

Objectives:To investigate the effect of the addition of glass flakes on physical properties of conventional heat cure denture base resins and to compare it with a high impact strength denture base resin.Materials and Methods:Test specimens were divided into Group 1 - poly (methyl methacrylate) (PMMA) (Trevalon), Group 2 - Trevalon HI, Group 3 -5% glass flake +95% PMMA (Trevalon), Group 4 -10% glass flake +90% PMMA (Trevalon), and Group 5 -20% glass flake +80% PMMA (Trevalon). For glass flake modified groups, part of PMMA (powder) was substituted with the same weight of glass flake (GF003 m) as required, to bring it to 100% powder. Flexural strength was tested using three-point bending test and impact strength with Izod type impact tester.Results:Plain PMMA (Trevalon), showed the highest value of flexural strength followed by Trevalon HI. Trevalon HI (highly cross-linked PMMA) group showed the highest value of impact strength.Conclusion:Flexural strength of unmodified PMMA denture base resin decreases with increase in the concentration of glass flakes. Impact strength does not show any significant change at 5% concentration of glass flakes and impact strength significantly reduces with the addition of glass flakes in 10% and 20%.

LAZER UYGULAMALARININ PROTEZ KAİDE TAMİRİNİN DAYANIMINA ETKİSİ

Purpose: The aim of this study was to investigate the effect of Er;Cr;YSGG laser treatment with different energy levels before sandblasting and grinding on the transverse strength of denture base resin repaired with autopolymerizing resin. Material and Methods: A total of seventy rectangular specimens (65X10X3.3 mm) were prepared from heatpolymerized acrylic resin, which was repaired with autopolymerizing resin following conditioning methods: a) without surface treatment (control) b) grinding, c) sandblasting, d) Er;Cr;YSGG laser at 3 W-20 Hz + grinding, e) Er;Cr;YSGG laser at 3 W-20 Hz + sandblasting, f) Er;Cr;YSGG laser at 4 W-20 Hz + grinding, g) Er;Cr; YSGG laser at 4 W-20 Hz + sandblasting. The transvers strength was measured by a three-point bending test using a universal testing machine. Data were analyzed using 1-way ANOVA and Tukey’s Post Hoc test (p<0.05). Results: Er;Cr;YSGG laser application at 4 W-20Hz before sandblasting occured significantly higher values (30.48±7.66 MPa) when compared to the control group (15.48±4.32 MPa) (p<0.001). Grinding demonstrated the lowest values (9.38±4.62 MPa) among all the groups. Sandblasting showed significantly higher values than grinding (p<0.01). Laser application at 4W-20 Hz + sandblasting demonstrated significantly higher strength values than sandblasting alone (p<0.05). Conclusions: Surface pretreatments before repairing significantly affect the transvers strength of repaired denture base resin. Er;Cr;YSGG laser pretreatment at 4 W-20Hz before sandblasting may be useful to increase the transvers strength of denture base repairs